The present invention is directed toward a personnel lifting or lowering system and, more particularly, toward such a system which utilizes a plurality of pulleys. The system can be used by a worker for lifting or lowering himself or herself to or from an overhead position or could be used by other workers to lift or lower an injured worker or substantially any other load.
In a wide variety of construction and/or repair projects and in many other situations, it is often necessary to lift or lower a substantial load through a vertical distance. Not infrequently, a worker may become injured while working underground and must be lifted to ground level. Similarly, a worker who may become injured while working at an elevated position may have to be lowered to safety. The present invention is particularly suited for rescuing an injured worker by lifting or lowering him or her.
One of the more common ways of lifting or lowering an injured worker is through the use of a winch or the like. While winches may be effective in certain situations, there are other times when they are of little use. A winch must be mounted at a fixed position and there must be a worker at that fixed position to operate the winch. Thus, if a worker is injured at a lower position and the winch is located at an elevated position, any worker assisting the injured person must first climb up to the elevated position in order to operate the winch. Furthermore, there are times when a workman may wish to raise or lower himself and may be physically capable of doing so but cannot do so with a fixed winch-type system.
Pulley systems have also been utilized over the years to lift or lower injured workers or other loads. Such conventional pulley systems, however, can be rather dangerous and can result in even more serious injuries. Conventional pulley systems have no braking systems or the like to prevent a free fall in the event that a worker accidentally releases the end of the rope. Furthermore, although the pulley system may offer some mechanical advantage, the amount of effort involved in operating the same can still be great.
Systems have been proposed which are intended to improve on conventional pulley systems that have previously been available. International Safety Equipment Inc., of Devault, Pa. for example, offers a personnel lifting and lowering system under the name System "99". The System "99" is arranged and functions in a manner similar to a conventional pulley system but includes a capstan/roller drum at the upper portion thereof. The roller drum can rotate in only the lifting direction and is provided with means for preventing rotation in the lowering rotation. The lifting rope is wrapped two and a half times around the stationary drum to thereby provide a friction braking action when a load is being lowered.
While the ISE System "99" may provide some benefits over conventional pulley systems, it may still not be fully satisfactory. Among other things, the use of a capstan/roller drum may add unnecessary weight to the system. Furthermore, the System "99" does not include a braking means or the like for preventing free fall.
Also available on the market is the GRIP-TECH rescue system by Grip Safety & Rescue Systems Corp., of West Seneca, N.Y. The GRIP-TECH system is similar to a conventional pulley-type system but includes a brake or automatic fall arrester which locks the rope when a predetermined descent speed is sensed. While this may provide some additional safety, it does not provide the advantages of a constantly applied reverse brake which would allow a worker to let go of the lifting rope at any time without allowing for any significant movement of the worker being raised.